Optical measuring systems for measuring objects in a three-dimensional manner that use a lens array, for example a grid of microlenses having round lenses, are known from the prior art.
WO 00/08415 A1 describes, for example, a measuring system for measuring objects in a three-dimensional manner via a matrix of light points projected onto the object. The design of the measuring system is confocal and the matrix of light points is, for example, generated via a microlens array.
A similar optical measuring system having a confocal design for three-dimensional measuring is known from EP 0 485 803 A1, in which a lighting grid is described that is generated via a lens array.
Lens arrays frequently comprise round lenses arranged, for example, in a square or hexagon pattern and therefore have spaces between the individual lenses. These spaces are often made of the same material as the lenses and therefore are often also transparent such that light can also penetrate them. For example, with a flat surface of spaces and orthogonal impingement, this light passes unbroken through the spaces, while light that impinges orthogonally onto the lenses of the lens array is diffracted or focused towards their respective focal point by said lenses. Therefore, the light that impinges on the spaces does not follow the desired light path through the lenses of the lens array. However, if this light remains in the light path or measuring system, it can adversely affect the imaging quality of the measuring system.
To prevent the illumination of the spaces and thus the occurrence of interfering light, the spaces can, for example, be coated with an opaque coating. This can prevent light from being transmitted through the spaces.
If the spaces are coated with an absorbent surface, it is possible to largely or even almost completely absorb the impinging light.
However, the spaces can also be coated with a coating that reflects light off to the side or filled with an appropriate medium. For example, a coating of microstructures, such as reflective cones or pyramids, can be provided, through which the impinging light is blocked out or directed out of the light path.
Known examples of coatings for spaces in lens arrays include chromium or chromium oxide coatings.
However, one disadvantage of the coating of the spaces is the additionally necessary process step of coating that leads to additional costs for the production of the lens array.
Depending on the coating, it can also be that the impinging light is not fully absorbed on the coating or reflected in the desired direction but is at least partially reflected diffusely or scattered. As a result, this light remains in the system and as scattered light adversely affects the imaging quality of the measuring system. Scattered light refers to light that does not follow the desired light path but propagates diffusely through the measuring system.
Furthermore, there is also the possibility of avoiding the spaces entirely by designing the lens array with square lenses. However, manufacturing such lens arrays is more laborious and therefore more expensive.
An optical configuration is known from US 2007/0296956 A1 that makes it possible to remove beams that are not diffracted by an object to be measured and would falsify the measurement result from a measurement beam path via an absorbent means.
It is therefore the object of the invention to provide an optical measuring system having a lens array that does not have any of the aforementioned problems and disadvantages.